I have an old dell sitting around. But I agree with BG, it's hard to upgrade. The only memory that I could get for it was from Dell, and it was 3x more expensive than the standard memory on the market.
Also, a friend of mine asked me to recommend a pc for her son. I recommended one of those prebuilt Kits so it had standard parts (not Dell propriatary stuff). Of course she ignored my advice, and got him a slim case Dell. The first thing he did was buy a better graphics card, which is too big for the case, so he can use it, but he cannot close his case now.
Bucky, you could look at something like this:
http://www.tigerdirect.com/applications/category/category_tlc.asp?CatId=31&name=Barebones